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Owner Ferrovie Trenord, Milano
Engineering Studio I.R. Ingegneri Riuniti - Ing. Giuseppe Barbagallo, Catania
Construction SALCEF Spa, Roma
Waterproofing Drytech Italia, Montano Lucino
Drytech Tank 1.800 m²
RAILWAY UNDERPASS, SARONNO / How can you open a new road without closing another? The route of a new stretch of the Trenord railway intersects the Milan-Varese railway line near Saronno Sud. The underpass enabling the intersection was built without interrupting rail traffic on the line above.
The technique adopted was the top down or Berlin method (retaining wall system). Firstly, micropiles were installed in the ground to create the retaining walls of the two supports of the underpass. A stretch of one of the two tracks of the line above was then removed, directing the traffic onto the other. A narrow strip was then dug and lean concrete was cast, protected by cellophane. The concrete bed was then cast using Drytech waterproof concrete in support of the micropile retaining wall. The concrete bed was prepared using DRYset crack inducers which were laid inside the reinforcement. The whole operation was carried out in only three days, at the end of which the track was reopened.
The procedure was then repeated on the other track, directing the traffic onto the first track. After another three days the line returned to normal capacity with both tracks open.
Digging was then carried out under the concrete bed, which at this point became the slab supporting the tracks. The lean concrete was demolished and the cellophane sheet was removed. In the meantime the concrete bed for the tracks through the underpass was cast. Drytech laid the DRYset channels for injecting the joints of the slab/walls and concrete bed/walls. Once reinforcement in the walls was installed, the concrete lining was cast directly against the micropiles.
For this underpinning casting, special telescopic formwork equipped with a network of inlets was used. At the end of the concrete’s curing period, joints, bore holes and crack inducers were injected with DRYflex Resin which expands and seals through pressure.
Drytech Engineering provided advice concerning waterproofing aspects, collaborating with the structural engineer in the underpass’s planning phase.


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